1. Field of the Invention
The present invention relates to liquid droplet jetting apparatus which jets liquid droplets from a plurality of nozzles.
2. Description of the Related Art
As a liquid droplet jetting apparatus which jets liquid droplets from a plurality of nozzles, image recording apparatus is known. The image recording apparatus performs printing on a recording paper by jetting ink droplets from an ink-jet head installed on a carriage which is guided by a guide member to move reciprocatingly in a predetermined first direction.
Here, the plurality of nozzles formed in the ink jet head generally form a plurality of nozzle rows each extending in a second direction perpendicular to the first direction. However, because errors and the like may occur at the time of installing the ink-jet head onto the carriage, the nozzle rows are sometimes inclined with respect to the second direction. Then, under the condition that the nozzle rows are inclined with respect to the second direction, if ink droplets are jetted with the same timing as applied in the case that the nozzle rows are arranged in the second direction in order to print straight lines extending in the second direction, the landing positions of the ink droplets jetted from the nozzles which are formed on one end side in the extending direction of the nozzle rows and the landing positions of the ink droplets jetted from the nozzles which are formed on the other end side in the extending direction of the nozzle rows will deviate in the first direction each other. As a result, it is not possible to print straight lines extending in the second direction, and thereby the print quality may degrade.
In view of this, the image recording apparatus described in U.S. Patent Application Publication No. 2005/0196214 (corresponding to Japanese Patent Application Laid-Open No. 2005-246933), for example, changes an angle of the carriage to adjust the posture of the carriage so that the nozzle rows may become parallel to the second direction. In this image recording apparatus, a first convex slide portion and a second convex slide portion are provided on the carriage per se, and slide along a slide surface (a guide surface) provided on the guide member to be guided in a scanning direction. Here, the first convex slide portion is fixed to the carriage, whereas the second convex slide portion is movable in the second direction perpendicular to the first direction by virtue of a posture adjustment means. Then, it is possible to change the angle of the carriage relative to the first direction by moving the second convex slide portion by the posture adjustment means and adjusting a positional relationship between the first and second convex slide portions.
The posture adjustment means includes an adjuster block configured integrally with the second convex slide portion, an eccentric round shaft fitted or inserted into the adjuster block such that its outer circumferential surface is in touch with an abutment surface of the adjuster block, a circular dial plate formed integrally with the eccentric round shaft, a plate spring arranged to face the dial plate, and the like. Then, by turning the dial plate to rotate the eccentric round shaft, it is possible to change the position of the outer circumferential surface of the eccentric round shaft and to move the adjuster block in touch with the eccentric round shaft integrally with the second convex slide portion.
Further, a plurality of grooves are formed in the dial plate to align in the circumferential direction, while a projecting press portion is formed in the plate spring to be selectively engageable with any of the plurality of grooves. By virtue of this, it is possible to selectively position the eccentric round shaft formed integrally with the dial plate to any of a plurality of positions associated with the plurality of grooves of the dial plate.
Here, the longer the nozzle rows extend, the more the print quality degrades due to the inclination of the nozzle rows as described hereinabove. That is, in the case of long nozzle rows, even if the nozzle rows are inclined only a little, the landing positions of the ink droplets jetted from the nozzles on one end side in the extending direction of the nozzle rows and the landing positions of the ink droplets jetted from the nozzles on the other end side may greatly deviate each other in the first direction, and thereby the print quality may greatly degrade. Therefore, in such a case, it is necessary to finely adjust the direction of the nozzle rows. Then, in order to finely adjust the direction of the nozzle rows with the posture adjustment means described in U.S. Patent Application Publication No. 2005/0196214, it is necessary to form more grooves in the dial plate, or to reduce the eccentricity of the eccentric round shaft.
However, because the dial plate is a small component, it is difficult to increase the number of the grooves formed in the dial plate. Further, if the dial plate is enlarged to allow more grooves to be formed, the entire apparatus is also bound to increase in size. On the other hand, reducing the eccentricity of the eccentric round shaft narrows the movable range of the adjuster block (the second convex slide portion). Thereby, when the nozzle rows are greatly inclined, it may become impossible to adjust the direction of the nozzle rows.